Sustained action nitrogen fertilizer

ABSTRACT

APPLICATION TO SOIL OF A FERTILIZING AGENT WHICH COMPRISES NITRILOTRIACETONITRILE AS SUBSTANTIALLY THE SOLE SOURCE OF NITROGEN IN AN AMOUNT TO PROVIDE BETWEEN 0.001 AND 1.5 TONS OF ELEMENTAL NITROGEN PER HECTARE.

Patented Mar. 26, 1974 SUSTAINED ACTION NITROGENIIQER'IILIZERJI RudolfKeller, Ziegelhausen, and Edmund Holfmann and Walter Neugebauer,Constance, Germany, assignors'to Deutsche JGoldund.SiIbervScheideanstalt vorn'ials Roessler, Frankfurt am Main; Germany ENo-Drawing. Continuation-impart of abnn dqnedapplicaw tion Ser. No.827,470, May 9, 1969.v This application Jan.26, 1972, Ser. No. 221,043 yClaims'priority, application Ge man May 11, 1968,. P 17 67152.1 1 Int.Cl."C05f 11/00 U.S. Cl. 71--27 I cam ABSTRACT oF TH nrsCLosURE p iApplication to 'soil-lof 'a fertilizing agent vwhich comprisesnitrilotriacetonitrile as substantiallythe sole source of nitrogen in anamount to provide between 0.001' and 1.5 tons of elemental nitrogen perhectare. l

CROSS-REFERENCE TO RELATED APPLICATION This application is acontinuation-in-part of application' Ser. No. 827,470 and now abandoned,filed by the same inventors on May 9, l969'inrespect of Sustained ActionNitrogen Fertilizer. BACKGROUND OF THE INVENTION The invention relatestoapr ocess of furnishing a susplant. I p M As is. now common knowledge,plants require a sufiicient supply of mineral'nutrientsfor their;optimum de velopment. Essential nutrient s includeboth the basic, majornutrients, such as l-" K, 'N or -S aswell as the minor or trace elementnutrients, such as Mn, Cu, Zn, Fe or Mo." Io obtain a desirable plantgrowth, it is'e'ssenf tial that these nutrients are available in anadequate amount andin a form permitting acceptance by'the plant tainedaction nitrogen' fertilizer and trace elements to; the 4 during theentire vegetationperiod. I I Howeventhe' ideal conditions are very oftennot present in practical use since, on one hand, many nutrients, becauseof small solubility or small solubility of their derivatives, are notextracted 'in suflicient amounts by the water from the soil and, on theother hand, since the plant can only receive dissolved substances,readily solublesubstances are often washed out prematurely by excessiveamounts of precipitation. f To prevent that nitrogen fertilizers'arewashed out by atmospheric precipitation condensation products ofsomewhat lower solubility such as urea and urea-aldehyde condensationproducts are frequently employed as slow act ing fertilizers. Thenitrogen" content of'these products is between about 25 and 40% byweighhThis type of fertilizer however has no effect on the supply-ofthe' so-ca1led minor or trace nutrients to the plant andb'esides' 'itssolubility is too high to resist -rain and other atmospheric action forlonger periods of time. p 1

It has also been proposedto make thetracenutrients elements. In case ofphosphates of low solubility, such as iron'o'r manganese phosphate, thisprocedure will supply the plant, by decomposition of the soil, both withthe trace elements iron or manganese and with the major or basicnutrient, phosphorus.

But these polyaminocarboxylic acids have been found to be poor suppliersof nitrogen and on occasion to be even harmful to plants since theacidsformed by these fertilizers arenot sutliciently decomposed in the soil.This is due to the chemical structure of the polyaminocarboxylic acids.

T oobtain a slow release nitrogen fertilizer it has also beenproposed touse a source of nitrogen such as urea, and to add theretonitrilotriacetonitrile (NTN), a mono amino compound. In this combinationhowever the nitrilotriacetonitrile was only used to act as a releaserethat are present in the soil'in a form of low solubilityPolyaminocarboxylic. acids which are well known-from analyticalchemistry as strong chelate complex forming agents convert the compoundsof low solubilities .such as phosphates, carbonates and oxides intosoluble. form and thus make them available from'the s oil; They thusprovide the plant with soluble compositions ofthe trace tardant. Themain source of the nitrogen was the urea or similar compound whichtherefore had to constitute the by far larger portion of thecomposition. The amount of nitrilotriacetonitrile was strictly limitedsince it was J feared that otherwise the nitrile would impair theadequate nitrogen supply, which was to come from the urea.Unfortunately, urea by itself has too high a solubility. Therefore theretardation of the: release obtained with this combination was quiteinsufficient, particularly where the fertilizer was intended to lastthroughout one or several vegetation periods upon a single applicationonly. The reason why generally, the nitriloacetonitrile was believed tobe inadequate to furnish the necessary nitrogen supply was that it wasconsidered to undergo a similar' development in the soil as thepolyaminocarboxylic acids.

Surprisingly, it has now been found that nitrilotriaceto nitrile whenused as the sole nitrogen source can provide a suflicient supply ofnitrogen together with an extremely slow release action.

SUMMARY OF .THE INVENTION The invention accordingly resides in afertilizing process in. which nitrilotriacetonitrile is used assubstantially the sole source of nitrogen.

The invention also embraces a fertilizing agent in whichnitrilotriacetonitrile is combined with a plant nutrient and from 5 to20% by volume of a finely divided large surface silicicacid. v p

DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS The invention isbased on the finding that by the process proposed even a singleapplication of the fertilizer can furnish an optimal supply of nitrogento the plant during one or several vegetation periods and additionallywill also make the minor or trace nutrients available to the plant. Asalready indicated this is due to the fact that thenitrilotriacetonitrile is subject to hydrolysis under the action of thesoil humidity and thus is slowly converted to thewater soluble ammoniumsalts of the corresponding acid. The plant is thus supplied in acontinuous manner with small amounts of nitrogen and of the tracenutrients that are essential for plant growth. These trace elementsbecome available in the soil by conversion of the substances of lowsolubility to highly soluble compounds by means of. the correspondingaminopolycarboxylic acid whichfis formed during the hydrolysis and whichc0nsti tutes'a chelate complexforming agent.

The nitrilotriacetonitrile (NTN) has a high nitrogen content, i.e,a'content of 41.8% by weight. It is only slowly dissolved'by" rain afterbeing embedded in the soil and thus is only slowly passed into the upperlayers of the soil because" of its low'water solubility. It is nottherefore washed out rapidly as is the case with nitrogen mineralfertilizers of high solubility such as urea. Its low solubility, on theother hand, prevents also the formation of a too highly concentratedsolution in case of insufficient precipitation which might otherwiseresult in necrosis and burning of the plants.

That the addition of nitrilotriacetonitrile does not have any negativeeffect on the plant growth and does nqt inter-. fere with the soil floraand fauna was all the more sur prising and unexpected since nitriles arecommonly con.- sidered poisonous because of their relationship tohydro-' cyanic acid. Actually, the double action of the hydrolysisproducts of NTN which is of such value to the'plant growth is in no wayaffected by the chemical nature of the compound. H

NTN, similar to the other sustained-action nitrogen fertilizers, ispreferably employed in amounts between 0.001 and 1.5 tons of elementalnitrogen per hectare (2.471 acres). The upper limit depends however onthe type of plant for which the fertilizer is used. The fertilizer canbe used either prior to the seeding and planting of the plants or lateras a top dressing.

NTN can be made at comparatively low cost from rather inexpensive rawmaterials with present mechanical methods. It can for instance be formedby reacting ammonia with hydrocyanic acid and formaldehyde.

It has also been found that NTN has a beneficial effeet in the form ofan increase of the fertilizer actionof certain conventional fertilizers,if it is employed in combination with, for instance, quick-actingfertilizers, such as phosphates. I

If the problem is to treat a soil in which the trace nutrients areentirely absent, a combination can be used of NTN with substances of lowsolubility which contain the trace nutrients and will thus make thesetrace elements available to the plant throughout the entire vegetationperiod. Of particular usefulness for a combination of this type is forinstance Thomas phosphate slag.

A still further increase of the sustained action or slow release can beobtained by mixing the NTN in powdery form with a known release retardersuch as finely distributed silicone dioxide containing large surfacematerials in amounts from to 50 vol. percent. The effect of thisaddition is due to the high sorption action of the SiO,; for liquid orgaseous decomposition products. This mixture is of particular valuewherever the fertilizer is applied to a highly water permeable soil.

Preferred as large-surface materials are for instance silicic acids thatare obtained by wet precipitation or simi larly obtained silicates orsilicic acids which are obtained by a pyrogenic process. These types oflarge-surface materials are well known today as fillers in polymericmaterials and elastomers and as thickeners in liquids such as lacquers,solvents, etc.

It is preferred to employ the NTN, with or without additives, in theform of granulates in particular in pearl form. The granulates can beobtained from the molten stage, from a solution or by pelletizing. Byvarying the ratio of grain size to surface in the sustained actionfertilizer, the rate of dissolution of the fertilizer under the actionof water in the form of rain or soil humidity can easily be controlled.

A controlled, graduated sustained action can furthermore be obtained byadding a component having a water solubiilty substantially differentfrom that of the NTN. Such additives are for instance water repellentsilicones.

The possibility to vary the slow release effect in case of sustainedaction fertilizers is of particular interest in view of the widedivergence of requirements in agriculture and forestery. Thus, anextremely slow release of the effective agents to the soil is desirablein forest fertilizing, where an annual repetition of the fertilizingprogram is too expensive if large forest areas are involved.

timber production only in a' number of years because'of thecomparatively slow growth of the tree flora. However,

It will be understood though that the results of i the fertilizing offorests has been carried out on a large scale already in Scandinaviancountries and in South Africa and has had remarkable success there.Efforts in central Europe are mainly concerned with coniferous trees,particularly fir and pine trees, and more recently with Douglas firsand, .insofar as deciduous trees are concerned, with poplar trees.

. The essential nutrients. which must be supplied to the forest soil areN,--P and Ca, nitrogen being themost important element. In ordertoobtain an optimum metabolic process in the leaf, it is preferable andcustomary to add nitrogen to the soil together with phosphorous. Theusually employed fertilizers in'this case are superphosphate, potassiumammonium nitrate and urea. The results, particularly in case of urea,were not as desired because too much of the material was washed out byprecipitation. This brought about a demand for a fertilizer with longsustained action;

. So far the materials available for this purpose were mainly ureacondensation resins. However, the process of making these materials,particularly in the .case of polymeric urea-formaldehyde resincompositions, does not produce uniform quality. On the other hand, withother materials such as crotonylidene diurea resin the cost is too highfor use as a forest fertilizer because of the large amounts of materialrequired. In addition, not every "sustained action fertilizer is suitedfor fertilizing forests becauseof the special composition of forest soilwith its high humus content.

The nutrients and trace elements are bound in complexes by the polymerichumic acids in the humus and can be received by the root only with greatdifficulty. It is therefore desirable to have a sustained actionfertilizer which can prevent or reduce the binding action of the humicacids.

In this respect it has been found that since nitrilotriacetic acid, theintermediate product in the NTN de gradation, has the property offorming complexes it is thus possible to bring the substances intosolution which are normally tied down by the weaker humic acids, aprocess called mineralization. These substances can then be supplied tothe roots of the trees.

Although the nitrilotriacetic acid formed in the nitrile hydrolysis isnot subject to unlimited storage in the soil but in turn, is subject tomicrobial decomposition, its decomposition'rate is slow. The half-timeof the decomposition is about days. The fact that the nitrilotri aceticacid is formed in the nitrile hydrolysis only at a slow rate of speedassures that the plant remains sup plied throughout the entirevegetation period or several such periods with the necessary tracenutrients.

The process of the invention is therefore particularly useful for forestfertilizing to provide both a sustained action nitrogen fertilizer and amineralizor. This applies in particular to the product when used inpearl form, since in this form the product has a slow rate ofdissolution because of the small ratio of surface to volume and alsobecause of its smooth surface. This makes the. material particularlydesirable for spraying from an. airplane which.requires penetrationthrough foliage.

The excellent fertilizer action of NTN can easily b shown by simpletests with potted plants. The test plants in the following experimentswere the so-called German Weidelgras. (Loliumperenne L.) and oats. Incase of the grass, harvesting was effected several times during onevegetation period. This permitted to trace the sustained action of thefertilizer. The tests with oats, on'the other hand, showed the excellentaction on NT with regard to grainproduction.

The'tests in' each case were carried out with an average and with a leangarden soil in order'to show thecomplex formation of the nitrile.

EXAMPLE 1' Equal amounts of grass seed were planted into a series ofpots of even size in the middle of May. Thenitrilotriacetonitrile wasthen added after about 5 weeks in an amount corresponding to 0.5 ton ofelemental nitrogen per hectare of soil (2.471 acres). i

The water supply was adjusted to an amount of 60% of the maximum waterabsorptive capacityof the soil. The test period lasted until November,and during this period there were effected three cuttings. Theproduction obtained is shown in the following Table 1.

The table shows that the use of nitrilotriacetonitrile results in aproduction increase compared to the control test of between 2 /2 and 3times. The production figures in the table are stated in grams offreshly harvested substance per flower bud.

EXAMPLE .4

order to compare the slow-release effects of nitrilo-j triacetonitrileNTN), ethylenediaminotriacetonitrile (EDTN) anddiethylenetriaminopentaacetonitrile (DTPN), the fOllOWing' testswerecarried out with German Weidelgras (Lolium perenne L.) in flower pots.

The fertilizer was applied as a granulated top dressing in two differentseries distinguished by the amount of fertilizer. One series involved0.226 g. N/pot whiletheother series involved 0.439 g. N/pot. Each serieswas washed three times with an excess of water. The amount of'water wassuch that in each case about 300 ml. of water were drained from eachpot. There was also a control test in which unfertilized pots were used.These were not subjected to any washing with water.

TABLE 1 v Production First Second Third cutting cutting cutting SoilTest compound July 19 Sept. 8 Oct. 26

Average garden soil Control. (without N-fertilizer). 14. 8. 2. 7Nitrilotriacetonitrile 51. 9 17. 0 6. 9

Lean garden soil Control (without N-fertilizer) 11. 6 p 7. 5 2. 9

Nitrilotriacetonitrile 37. 6 13. 3 5. 9

EXAMPLE 2 The general-lay-out of the tests was as follows:

The nitrilotriacetonitrile was added in the test series of 30 Apr. 21:seeding of about 0.75 g. of seed of German this example to an averageand lean garden soil in an amount corresponding to 0.4 g. of elementalnitrogen per liter of soil and this was done prior to the planting ofthe plant which was German Weidelgras, a type of grass which haspreviously been identified by its Latin name.

The seeding was effected in the third week of July. The grass was cutaltogether twice and weighed each time. The production in grams is shownin the following Table 2.

The table shows the excellent effects of the nitrile upon the plantgrowth.

TABLE 2 Production First Second cutting cutting Soil Test compound Sept.8 Oct. 26 Total Average garden soil Control (without N -fertilizer) 7.4. 1 11. 1 Nitrilotriacetonitrile 15. 0 17. 2 32. 6

Lean garden soil Control (without N-t'ertilizer) 10. 1 4. 0 14. 2Nitrilotriacetonitrile 13. 3 18.3 31. 2

Sept. 14/ 15: third washing EXAMPLE 3 Oct. 13/14: fourth cut.

The plant tests in this example were carried out with The followingtable shows the production obtained in grams of hay per pot.

oat as the test plants and otherwise followed the same lay- TABLE out asExample 1. Nitrilotriacetonitrile was added in this [Relative we'ghtscollected] case also about 5 weeks after planting. The amount of 0 L 1 2mtrrle likewise corresponded to 0.5 ton of elemental nitro Nitrogen JuneJuly Sept? Oct? gen per hectare 2 471 acres) f L (gJpot) Fertilizer22/23 21/22 7/8 13/14 Total The oat was cut and dried 98 days after theaddition Ng t g 33.4 16.4 26.4 23.8 100 of the nitrile and 13 da seed'n5 Y5 aflier 1 The productfon 0226 NTN 35.1 24.4 59.2 15.2 134.0 m gramand stalks (straw) is shown m the following lggg 81.1 14.9 26.8 19.292.2 Table 3. The production figures are stated in grams of 0 439 TN 2119's dry substance per flower bud. I EDTllI-I: 174-4 3 07.2 DTPN...36.3 21.0 41.3 23.8 122.4

TABLE 3 Production Soil Test compound Grain Stalks Average garden soilControl (without N-tertilizer) 2. l 4. 4 Nitrilotriacetonitrile a. e 7.7

Lean garden soil Control (without N-fertilizer) 1. 2 2. 7Nitlilotriacetonitrile 4. 9 6. 9

as nitrogen fertilizers. No separate nitrogen supply was added.

In one case, that of EDTN, it will be noted that there even occurred adecrease of the yield as compared with the non-fertilized plants. OnlyNTN resulted in a substantial increase of the production. This wasparticularly the case where a larger amount of the fertilizer was usedin order to supply the stated larger amount of nitrogen.

From these tests, it can only be concluded that EDTN and DTPN are by farnot as active in their slow ,nitrogen release as NTN. It is believedthat this is due to too high a concentration of EDTN and DTPN or metalchelate compounds formed thereby. This in turn is undoubtedly due to thefact that the acids formed by these latter two fertilizers are notdecomposed or not decomposed sufliciently in the soil. This then causesa lower fertilizing,

efiect or may even have some damaging action, as compared with NTN whichis completely decomposed. To prove this point, the soil fertilized withNTN was examined at the end of the tests and it was found that onlytraces of the free nitrilo-triacetic acid could be found.

What is claimed is:

1. The process of improving the fertility of soil for an extended periodof time, which comprises applying to the soil a fertilizing agentcomprising nitrilotriacetonitrile in granular form as substantially thesole source of nitrogen in an amount to provide between 0.001 and 1.5tons of elemental nitrogen per hectare.

2. A process as defined in claim 1, in which the fertilizing agentcomprising nitrilotriacetonitrile in granular form is in the form ofpearls.

3. The process of claim 1, wherein the said fertilizing agent furtherincludes powdery finely divided large-surface silicic acidin an amountof 520% by volume rela tive to the amount of said nitrile.

4. The process of claim 3, wherein the large-surface silicic acid is awet-precipitated finely divided silicic acid.

5. The process of claim 3, wherein the large-surface silicic acid is afinely divided fume silica.

6. The process of claim 1, wherein the said fertilizing agent furtherincludes a water repellent silicone.

7. A fertilizer in granular form comprising nitrilotriacetonitrile asthe sole source of nitrogen, a plant nutrient and from 5 to 20%by'volume relative to the nitrile' of a finely divided large surfacesilicic acid.

References Cited UNITED STATES PATENTS 3,427,144 2/1969 Kapar 71--283,290,158 12/1966 Treat 71-62 X 3,679,391 7/1972 Jack et a1. 7164 ECHARLES N. HART, Primary Examiner R. BARNES, Assistant Examiner US. Cl.X.R. 7162, 64 F

